The objective is to understand the role of estrogen receptors in the regulation of uterine growth and function by elucidating the important receptor changes which occur concomitantly or are required for estrogen regulation of gene expression in target cells. This is to be accomplished by studying the steroid hormone-regulated expression of several recently characterized estrogen-dependent secretory rat endometrial proteins, correlated with estrogen-dependent receptor modulation in the same cells, documenting changes in the receptor protein with a library of monoclonal antibodies to the estrogen receptor as well as steroid binding methods. The estrogen-responsive, marker proteins of the rat endometrial epithelium will be isolated, purified and characterized and used for preparation of polyclonal and monoclonal antibodies. These marker protein antibodies will be used to identify the location and possible function of the proteins and to isolate the specific m-RNAs for the proteins. After preparation of c-DNA, detailed studies will characterize the nature of the regulation of the marker at the level of transcription and translation. The c-DNA will eventually be used to screen genomic libraries to identify the gene for the estrogen-dependent markers so that the molecular details of the receptor regulated expression of the marker can provide new insight into the estrogen regulation of gene expression in the uterus. Immunoblots, binding and fractionation studies as well as immunohistochemical assays with the monoclonal antibodies to the receptor will be used to characterize changes in the nature, content and localization of the estrogen receptor in the different types of uterine cells under various hormonal conditions. Immunomethods will be used to study the major receptor events, such as estrogen receptor synthesis, potentiation, activation, processing, recycling, degradation and receptor binding to chromatin and nuclear matrix. These studies can be expected to provide new information on changes in the estrogen receptor, not available simply from assay of estrogen-binding studies, and to improve our understanding of the molecular details of steroid hormone regulation of the individual cell types of the uterus at the molecular level. This new knowledge will be useful for better diagnosis and treatment of steroid hormone-dependent cancers and will provide useful information for the control of normal and abnormal reproductive function.